The present disclosure relates to an actuator.
The present invention concerns an actuator. More particularly, but not exclusively, this invention concerns an actuator comprising an actuator body, a piston moveable within the actuator body, and a rod attached to the piston and extending out of a first end of the actuator body, the actuator body comprising a port for conveying actuator fluid to or from the actuator body to effect movement of the piston and rod.
The invention also concerns an aircraft assembly, such as a landing gear assembly, comprising the actuator, an aircraft comprising the actuator and a method of operating an actuator.
Prior art actuators, for example actuators to effect movement of landing gear doors on an aircraft, often suffer from dynamic load peaks, such as when the piston of the actuator reaches the end of its travel in an actuator body or because of hydraulic peaks due to valve switching, dynamically generated loads or a hydraulically generated feature during actuator travel. The load peaks may occur when there is acceleration or deceleration of the piston. These load peaks can cause fatigue effects on both the actuator and surrounding attachment structure. This requires that the actuator and structure are designed to allow for these effects and may be bigger or heavier than otherwise required.
To overcome these problems, many actuators are provided with snubbing rings to reduce the load peaks at the end of piston travel. These snubbing rings, or other snubbing devices, restrict the flow of fluid in or out of an actuator, which minimises piston acceleration/deceleration at the end of travel. However, the response of the actuator can be detrimentally affected by the use of snubbing devices. In addition, the snubbing devices offer limited flexibility for design alterations and are not readily able to “fade” in or out—in other words, there are essentially either “on” or “off” and have limited or no “ramping” up/down capability. They also have a fixed performance and cannot easily be altered for different operating conditions (e.g. aircraft speed, fluid temperature etc.). Furthermore, failure in a mechanical snubbing device can be difficult to detect, so that failure exposes the actuator and airframe structure to high loads. The actuator and structure have to be designed to allow for these high loads after snubbing device failure.
The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved actuator.